1. Field of the Invention
The present invention relates to communication systems. More specifically, the present invention relates to data routing systems.
While the present invention is described herein with reference to illustrative embodiments for particular applications, it should be understood that the invention is not limited thereto. Those having ordinary skill in the art and access to the teachings provided herein will recognize additional modifications, applications and embodiments within the scope thereof and additional fields in which the present invention would be of significant utility.
2. Description of the Related Art
A data router is a device that accepts data in one or more formats from one or more input channels and routes the data to one or more output channels in one or more formats. A bursted data router is a data router with input and output channels formatted into groups of data symbols called bursts. Bursts are usually grouped into time-division multiplexed frames, with each burst in a frame numbered from 1 to N, for purposes of routing identification.
Routing takes place when a burst is moved from its source, e.g., input channel 1, 2 or 3 and input burst number 1 to N, to its destination, e.g., output channel 1 or 2 and output burst number 1 to N.
In more complex applications, each channel may carry different types of bursts, with each burst type having a characteristic length (number of symbols per burst) and period (time duration of each burst). Output bursts may be constructed of one or more input bursts, or just a fraction of an input burst. In the general case, a bursted data router must translate incoming data bursts into the required output burst format.
Input channels provide formatted data bursts to the router and output channels from the router provide formatted data bursts to connected communications devices such as transmission lines, modulators, and eventually to demultiplexers. One router output channel may eventually connect to many communications devices. Demultiplexers connected to the router output examine a specific area of a frame to extract the burst carrying data of interest. These devices generally expect the burst to be in a specific format. The router therefore functions as a multi-position switch and format translator, directing input data to its desired destination device and translating it into a specified format.
Bursted data routers take advantage of the known, predetermined period of each input burst to simplify routing. A small range of acceptable, selectable burst periods, lengths and timing are determined during router design. Typically, incoming bursts are timed such that their boundaries (where they start and stop in time) are aligned. By aligning incoming burst boundaries, access of each input burst to an output channel can be precisely and simply scheduled to avoid conflicts with other bursts. All incoming bursts arriving during the same burst period are accumulated in burst-sized input buffers. During the following burst period, the input buffers take turns accessing (transferring their data to) output channels. Each input buffer is assigned a fixed time interval within a burst period in which to access the output channels. Thus, collisions between two input bursts simultaneously trying to access the same output channel are avoided.
The restriction of the conventional bursted data router, to processing data formatted into time-aligned bursts, limits its application to rigidly controlled communications links. Many applications, such as satellite links, have non-bursted data with varying timing on some channels while other channels are bursted and time-aligned. In such applications, the need exists for a data router capable of routing bursted and non-bursted data.